The use of communication systems having wireless mobile communication units has become widespread. Wireless communication systems provide several important advantages over conventional wired systems. For example, wireless communication users can communicate in locations where wired service is not available or feasible, such as remote or rugged locations. Additionally, wireless communication users have much more mobility because they do not have to connect to a fixed wired network. These and other favorable characteristics make wireless communications ideally suited for personal, business, military, search and rescue, law enforcement, and water vehicle applications. The power of networking and collaborative, distributed computing is being realized in wireless mobile communication units. However, mobile networks provide many additional challenges not associated with fixed networks.
Several important mobility management issues need to be addressed in designing a communication system with a dynamic network topology having mobile access points and/or mobile network nodes with a relatively large number of mobile users. Critical issues with mobile management include tracking mobile users in the system, reaching and initiating communications with mobile users and continuity of service when a mobile user moves between coverage areas. Conventional networks do not provide solutions to these problems within their specific domains. In conventional systems, a network administrator needs to reconfigure the respective networks and/or networks to accommodate the entry of a new mobile user. For example, if a user moves a laptop computer from a first network to a second network, the second network will need to be reconfigured to assign a new address (e.g., (Internet Protocol (IP) address) to the laptop computer to accommodate for the domain name associated with the laptop. A system administrator will have to then enter the domain name into the domain name server (DNS) for the second network and remove the domain name from the DNS of the first network. Both the first network and second network will then have to be rebooted to complete the configuration.
In mobile network environments, capabilities are required for allowing nomadic users to migrate from one logical network or sub-network to other logical networks or sub-networks without human interaction or network management interactions. Current solutions include Cellular Digital Pack Data (CDPD) networks, Cellular/Personal Communications Services (Cellular/PCS) systems, and Mobile Internet Protocol (mobile IP) networks. These solutions provide mobile users with fixed addresses or identifications and employ third party services to forward information destined for the mobile unit through one or more intermediaries to the network that the mobile user currently resides.
For example, mobile IP networks include mobile nodes, home agents and foreign agents. A home agent is a router that authenticates a mobile node, tracks a mobile user location and redirects data packets to the mobile user's current location. A foreign agent assists the mobile node in informing its home agent of its current location and routes data traffic sent by the mobile user. Similar to CDPD, mobile IP uses triangular routing. A mobile's home agent receives packets destined to the home address of the mobile user, encapsulates the packet and transmits the packet to the mobile node that the mobile user is currently residing. A mobile user must contact home in order to receive any services (e.g., e-mail, voice). The home agents are built into the network layer of a Transmission Control Protocol/Internet Protocol (TCP/IP) stack, and therefore, burdens the overhead associated with the network layer.
Additionally, the use of a home agent or third party service is impractical in some applications due to certain limitations. For example, recently the introduction of distributed denial of service (DDS) has become available to protect against users trying to access other user's systems and invoke destructive programs with fictitious names and addresses from the other user's system. Ingress filters detect packets launched with IP addresses not part of the transmitting packet and terminate this action. This terminates a mobile IP transmission since the mobile IP sent from the mobile user is foreign to the ingress filter. Furthermore, mobile IP is impractical for mobile tactical networks, since the node having the home agent can be destroyed eliminating any communication to the mobile node when it is at a visiting node.